I've found Cornwall to be bad for this. We were on holiday last year in Cornwall and it was pissing it down with rain so wanted to take the kids somewhere indoors. We'd seen the brown signs (in the UK, brown signs indicate a place of interest) for some "jungle barn" or something, thinking it was going to be an awesome place, but it turned out to be a normal run of the mill hellish soft play centre.

That Springfield Fun Park is actually quite decent for young kids though.